The present invention relates in general to penetrating radiant energy imaging and more particularly concerns novel apparatus and techniques for selectively obtaining X-ray images of variable density contrast and/or spatial resolution with a modification of commercially available MICRO-DOSE X-ray apparatus disclosed in U.S. Pat. No. 3,780,291, manufactured and sold by American Science & Engineering, Inc. The invention readily achieves magnification and greater resolution in the image of a scanned object with an improved scanning slit assembly.
The present invention represents an improvement of the invention in U.S. Pat. No. 3,780,291, embodied in the commercially available AS&E MICRO-DOSE X-ray imaging system used in airports and other locations for parcel inspection. In that system a moving pencil beam of X-rays repeatedly scans a line detector as the scanned object is translated past the beam and detector assembly. The line detector produces light signals representative of the incident X-ray energy, which are then converted by photoelectric detecting means to video signals representative of the X-ray transmissivity between the beam source and the detector. From the video signals, a video system displays a sequence of horizontal lines to provide a two dimensional image of the scanned object.
Four radial slits in a rotating disc of X-ray opaque material successively intercept the line beam to produce a pencil beam that scans the length of the line detector as the radial slits rotate; the intersection of one of the four slits and their corresponding line slit moves from one end of the line beam cross section to the other.
It is an important object of this invention to provide an improved X-ray imaging system.
It is another object of the invention to achieve the preceding object with a system that provides increased density contrast as a trade-off against the size of the area of the object being imaged.
It is still another object of the invention to provide an improved X-ray imaging system that provides increased density contrast without decreasing the area of the object being imaged by increasing the number of detectors.
It is a further object of the invention to achieve one or more of the preceeding objects with relatively slight modification of the prior art system described above.
It is still a further object of the invention to achieve one or more of the preceding objects by selectively displacing the relative position between the scanning slit assembly and the detector and X-ray source.
It is still a further object of the invention to achieve one or more of the preceding objects economically and with high reliability while permitting a relatively unskilled operator to easily effect the change in resolution/contrast.
It is still a further object of the invention to utilize essentially the same logic electronics for each of the images constructed using any of the line slit-radial slit combinations.
It is still a further object of the invention to have a fixed spatial relationship between the images formed by each line slit-radial slit combination, allowing a small area of one of the larger images to be easily X-rayed at higher density and/or spatial resolution.